From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 18 Mar 2016 15:28:04 +0000 (+0100)
Subject: tracing: Record and show NMI state
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=7e6867bf831c71fe0e47438831ae3a94d4c7ab3c;p=linux.git

tracing: Record and show NMI state

The latency tracer format has a nice column to indicate IRQ state, but
this is not able to tell us about NMI state.

When tracing perf interrupt handlers (which often run in NMI context)
it is very useful to see how the events nest.

Link: http://lkml.kernel.org/r/20160318153022.105068893@infradead.org

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index cb2b708e4ea76..7bdf8ba323ec8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1664,6 +1664,7 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
 #else
 		TRACE_FLAG_IRQS_NOSUPPORT |
 #endif
+		((pc & NMI_MASK    ) ? TRACE_FLAG_NMI     : 0) |
 		((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
 		((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
 		(tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) |
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 39588c23dd8b6..3fff4adfd431c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -125,6 +125,7 @@ enum trace_flag_type {
 	TRACE_FLAG_HARDIRQ		= 0x08,
 	TRACE_FLAG_SOFTIRQ		= 0x10,
 	TRACE_FLAG_PREEMPT_RESCHED	= 0x20,
+	TRACE_FLAG_NMI			= 0x40,
 };
 
 #define TRACE_BUF_SIZE		1024
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 282982195e09f..0bb9cf2d53e66 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -389,7 +389,9 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
 	char irqs_off;
 	int hardirq;
 	int softirq;
+	int nmi;
 
+	nmi = entry->flags & TRACE_FLAG_NMI;
 	hardirq = entry->flags & TRACE_FLAG_HARDIRQ;
 	softirq = entry->flags & TRACE_FLAG_SOFTIRQ;
 
@@ -415,10 +417,12 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
 	}
 
 	hardsoft_irq =
+		(nmi && hardirq)     ? 'Z' :
+		nmi                  ? 'z' :
 		(hardirq && softirq) ? 'H' :
-		hardirq ? 'h' :
-		softirq ? 's' :
-		'.';
+		hardirq              ? 'h' :
+		softirq              ? 's' :
+		                       '.' ;
 
 	trace_seq_printf(s, "%c%c%c",
 			 irqs_off, need_resched, hardsoft_irq);